In What’s Next? Time Travel and Phenomenal Continuity Giuliano Torrengo and Valerio Buonomo argue that our personal identity is about continuity of phenomenal experience, not such psychological matters as memory (championed by John Locke). They refer to this phenomenal continuity as the ‘stream of consciousness’. I’m not sure that William James, who I believe originated the phrase, would have seen the stream of consciousness as being distinct from the series of psychological states in our minds, but it is a handy label.

To support their case, Torrengo and Buonomo have a couple of thought experiments. The first one involves a couple of imaginary machines. One machine transfers the ‘stream of consciousness’ from one person to another while leaving the psychology (memories, beliefs, intentions) behind, the other does the reverse, moving psychology but not phenomenology. Torrengo and Buonomo argue that having your opinions, beliefs and intentions changed, while the stream of consciousness remained intact would be akin to a thorough brainwashing. Your politics might suddenly change, but you would still be the same person. Contrariwise, if your continuity of experience moved over to a different body, it would feel as if you had gone with it.

That is plausible enough, but there are undoubtedly people would refuse to accept it because they would deny that this separation of phenom and psych is possible, or crucially, even conceivable. This might be because they think the two are essentially identical, or because they think phenomenal experience arises directly out of psychology. Some would probably deny that phenomenal experience in this sense even exists.

There is a bit of scope for clarification about what variety of phenomenal experience Torrengo and Buonomo have in mind. At one point they speak of it as including thought, which sounds sort of psychological to me. By invoking machines, their thought experiment shows that their stream of consciousness is technologically tractable, not the kind of slippery qualic experience which lies outside the realm of physics.

Still, thought experiments don’t claim to be proofs; they appeal to intuition and introspection, and with some residual reservations, Torrengo and Buonomo seem to have one that works on that level. They consider three objections. The first complains that we don’t know how rich the stream of consciousness must be in order to be the bearer of identity. Perhaps if it becomes attentuated too much it will cease to work? This business of a minimum richness seems to emerge out of the blue and in fact Torrengo and Buonomo dismiss it as a point which affects all ‘mentalist’ theories. The second objection is a clever one; it says we can only identify a stream of consciousness in relation to a person in the first place, so using it as a criterion of personal identity begs the question. Torrengo and Buonomo essentially deny that there needs to be an experiencing subject over and above the stream of consciousness. The third challenge arises from gaps; if identity depends on continuity, then what happens when we fall asleep and experience ceases? Do we acquire a new identity? Here it seems Torrengo and Buonomo fall back on a defence used by others; that strictly speaking it is the continuity of capacity for a given stream of consciousness that matters. I think a determined opponent might press further attacks on that.

Perhaps, though, the more challenging and interesting thought experiment is the second, involving time travel. Torrengo is the founder of the Centre for Philosophy of Time in Milan, and has a substantial body of work on the the experience of time and related matters, so this is his home turf in a sense. The thought experiment is quite simple; Lally invents a time machine and uses it to spend a day in sixties London. There are two ways of ordering her experience. One is the way she would see it; her earlier life, the time trip, her later life. The other is according to ‘objective’ time; she appears in old London Town and then vanishes; much later lives her early life, then is absent for a short while and finally lives her later life. These can’t both be right, suggest Torrengo and Buonomo, and so it must surely be that her experience goes off on the former course while her psychology goes the other way.

This doesn’t make much sense to me, so perhaps I have misunderstood. Certainly there are two time lines, but Lally surely follows one and remains whole? It isn’t the case that when she is in sixties London she lacks intentions or beliefs, having somehow left those behind. Torrengo and Buonomo almost seem to think that is the case; they say it is possible to imagine her in sixties London not remembering who she is. Who knows, perhaps time machines do work like that, but if so we’re running into one of the weaknesses of thought experiments methodologically; if you assume something impossible like time travel to begin with, it’s hard to have strong intuitions about what follows.

At the end of the day I’m left with a sceptical feeling not about Torrengo and Buonomo‘s ideas in particular but about the whole enterprise of trying to reduce or analyse the concept of personal identity. It is, after all, a particular case of identity and wouldn’t identity be a good candidate for being one of those ‘primitive’ ideas that we just have to start with? I don’t know; or perhaps I should just say there is a person who doesn’t know, whose identity I leave unprobed.


  1. 1. Paul Torek says:

    But… but… but… phenomenal continuity IS (one kind of) memory. The stream of consciousness connects, and makes sense, only because memory connects it. Even short-term memory is still memory.

    “because they would deny that this separation of phenom and psych is … even conceivable.” Hear hear! That’s me.

    “This might be because they think the two are essentially identical, or because they think phenomenal experience arises directly out of psychology.” And later: “The second objection … says we can only identify a stream of consciousness in relation to a person in the first place.” No, none of these quite capture my objection. Phenomenal experience goes beyond propositional memory, habits, and personality traits – which seems to be what “psychology” means here. And we can make sense of fission thought-experiments, where one person becomes two and the stream of consciousness connects to both descendants.

    No, what’s wrong with the proposal is precisely that “*stream* of consciousness” (emphasis added) presupposes memory.

  2. 2. davidly says:

    I like these thought experiments because they concretize a notion I’ve had for I don’t know how long. Namely, that our stream of consciousness skips about from time and place. I could never reconcile this with the lack of continuity of experience and memory. Until now. The continuity is an illusion; the stream of consciousness is immediately attuned to the experience it occupies.

    I also think that when we fall asleep we do acquire a new identity. Or experience an different or substantially enough altered one. Why do I think any of this? I can’t remember. I’m sure it’ll come to me.

  3. 3. wtquinn says:

    Please add some drama and suspense.

    Hint: Terminator movies
    Hint: Undoing of personal and group remorse and regret.


    If you are first to market you’ll get all the merchandising rights.


  4. 5. Tom Clark says:

    The authors say “what is constitutive of personal identity over time according to the phenomenal approach is the fact that different experiences belong to one and the same stream of consciousness, regardless of the content of such experiences.”

    Agreeing with Paul in comment #1, it isn’t clear to me how phenomenal continuity as a criterion for personal identity is established in the absence of psychological continuity, e.g., memories, character, etc. which determine the content of experiences. Personal identity over time is predicated on being the same person over time, which involves at least some psychological similarities carried over from one moment to the next. A stream of a particular person’s consciousness can only be identified as that person’s continuous stream on the basis of psychological similarities over time.

    In contrast to the authors’ approach, I’d suggest that it isn’t personal identity that gets maintained by phenomenal continuity in their thought experiments, but a *generic* subjective continuity: the persistence of experience across different subjects. In a paper written a while back (linked on my name above), I use a Parfit-style transformation thought experiment to illustrate this, and then apply it to the question of what we should anticipate at death.

  5. 6. Tim says:

    @Tom Clark

    Basically generic subjective continuity (gsc) boils down to the universe being one yet many simultaneously (different aspects of the whole). And the sense of moving from one moment to the next is merely a mereological illusion of “caused” (b theorist) by a self-referential memory narrative of relational memory states. This make sense?

    Given the implications of this, this should imply that we should never anticipate not being a thing that doesn’t have subjectivity, as all things within everything, that don’t have subjective content, are “skipped”, in the sense that there’s no subject embedded in that spacetime region. This implying that we should anticipate, after death, experiences in various body incarnations, that being of the highest bliss, extreme torture, and all in between (unless there’s a transfinite zone in the universe that has indefinite subjectivity that is of a certain kind and within a certain threshold across many categories). This scares me knowing that I’m “x” body iterations from being skinned alive, countless times, for example.

  6. 7. Tom Clark says:

    Thanks Tim. I like “the sense of moving from one moment to the next is merely a mereological illusion of ’caused’ (b theorist) by a self-referential memory narrative of relational memory states.” And you’ve hit on the downside of there not being nothingness in store for us, namely all the possible states of suffering. Which is why the Buddhists hoped for cessation from reincarnation: accumulate enough merit and you won’t be reborn, congratulations!

  7. 8. Tim says:

    @Tom Clark

    Thanks for your reply. Coming to grips with there being no nothingness changed my life forever. How do the implications of gsc make you feel on a personal note? I have unfortunately seen a lot of graphic, violent videos on the interest that have deeply disturbed me, and the thought that this awaits “me” indefinitely after death is very traumatizing. How do you manage your sanity?

  8. 9. Tom Clark says:

    Tim (8), mostly I avoid violent videos and images whenever possible and do what little I can to reduce the prevalence of violence, for instance by promoting worldview naturalism as an antidote to our retributive inclinations. If death is, as I suggest, the radical refreshment of subjectivity, then the prime directive is to make all worlds safer and less punitive for conscious subjects. Also, make fewer of them – e.g., see Thomas Metzinger’s Benevolent Artificial Anti-Natalism (BAAN) at

    I’d be interested to hear how you came to the no nothingness conclusion (perhaps offline so we don’t take over this thread).

Leave a Reply